Chernobyl and public health

In 1992, when the first effects of the Chernobyl accident on the prevalence of thyroid cancer in children were reported,¹ they were met with scepticism by the radiological community.²,³ Some of this scepticism was undoubtedly scientific (“iodine-131 has a low carcinogenic potential”), though some was not. These reservations have now mostly been resolved by re-examination of the data on the relation of exposure to x rays and thyroid cancer and a realisation of just how many children were exposed. It is a cautionary tale of how scientific instinct can mislead: help could have been provided more quickly had it not been for this debate. Nevertheless, similar debates are now obscuring our ability to learn longer term lessons from Chernobyl and provide further help to its victims.

Some sceptics, relieved that the fallout had not originated and fallen in western Europe or America, where populations are litigious, were reluctant to concede that environmental sources of radiation could be strongly associated with serious disease. Childhood thyroid cancer has a very low spontaneous incidence in most countries (<1/1 000 000/year). Thus, the appearance of several tens of cases in the region round Chernobyl from a population of under half a million children, giving relative annual incidences of ⩾100/1 000 000, should have left little room for doubt that something was seriously amiss.

Today there is little dispute that a real increase in thyroid cancer occurred among young people in Belarus, the Ukraine and, to a lesser extent, the Russian Federation, and that it was associated with the Chernobyl accident.⁴ Indeed, in a recently published study of post Chernobyl cases⁵ the risk is found to fall within the confidence limits for the absolute risk for thyroid cancer after external radiation exposure,⁶ thus contradicting the widely held assuption that ¹³¹I is only weakly carcinogenic. This was apparently based more on lack of evidence than definitive findings. Perhaps it is no coincidence that one of the last bastions of this belief is in America, where deliberate releases of ¹³¹I were made from the Hanford complex in the late 1940s to study the behaviour of fallout clouds.⁷ More recently, we have learnt that weapons testing in the atmosphere over Nevada in 1950-62 appears to have left few parts of America unaffected by releases of ¹³¹I three to four times greater than those from Chernobyl.⁸ Neither is Europe without its weapons testing legacy. The Soviet Union has made extensive atmospheric tests in the Arctic, possibly the cause of the increased incidence of thyroid cancer reported in Norway.⁹

In America a report from the National Cancer Institute on the Nevada releases is currently being reviewed by the National Academy of Sciences and Institute of Medicine to assess the public health implications and advise the government on how to communicate these risks to doctors and the public. Had it not been for the dramatic increase in the incidence of childhood thyroid cancer in the Chernobyl region the health risk from the Nevada testing might have been dismissed as negligible, based primarily on the evidence for adults treated with 131I, which points to a very low risk.

Even so, questions remain about the health effects of ¹³¹I exposures. How far the risks seen in the former Soviet Union can be extrapolated to the American population is unclear. We still do not know how long the increased incidence of thyroid cancer will continue (12 years have elapsed since the Chernobyl accident), or the accident’s impact on thyroid conditions other than cancer and non-thyroid disease, such as breast cancer. These uncertainties serve only to emphasise the importance of the Chernobyl populations to our understanding of the health effects of such exposures.

However, the prospects for learning from the Chernobyl accident over the necessary time scale (the next 40 or so years) are bleak. Firstly, their economic and political upheavals have made it difficult for countries of the former Soviet Union to respond to the immediate public health problems of the increase, let alone conduct rigorous epidemiological studies. Secondly, the initial scepticism and acrimonious debate in the international scientific community did little to encourage collaboration between international agencies supporting either the humanitarian aspects or research. Thirdly, despite scepticism about the origin of the increased incidence of childhood cancer, a prominent aim of research has been to seek characteristics, at molecular level, that might signal radiation as the cause of the cancer. So far no such markers have been identified for any tumour. Such markers would have obvious benefits in helping to determine eligibility for compensation for radiation induced cancers, and this financially motivated aspect of the research has produced an unproductively competitive atmosphere in some research circles.

If the lessons of a disaster on the scale of Chernobyl are to be learnt an international effort is essential. For the results to be meaningful independence from vested interests must be guaranteed; the compensation issue in America and for the nuclear industry is potentially so large that significant sums could be spent to frustrate legitimate research in the hope of avoiding much larger sums in compensation. How can these two objectives be met?

After the atomic bombings in Japan a joint Japanese-American study was initiated and continues today as the Radiation Effects Research Foundation. It is the main source of knowledge about the effects of radiation on human health. The situation in Japan, involving only two principals, is simple in comparison with that in Chernobyl, where three independent states are involved together with tens of international, national, and private agencies. Nevertheless, if the opportunities to learn from this disaster are not to be irretrievably lost some kind of initiative along the lines of the Japan-American foundation is required. Improved coordination has been universally advocated over the past five or six years, yet the position has not improved. Either no one organisation commands both the authority and the confidence of the other organisations to allow it to coordinate effectively, or the participating organisations do not want to cooperate as their real aims differ from those they proclaim.

The humanitarian aspect to this problem should also not be forgotten. Whatever the decision about an international effort to learn about the course of the epidemic, speculative research to identify a marker of radiation causation will continue—because the rewards are so high. This research impinges negatively on the lives of those exposed and is rumoured to have led to a market in tumour tissue. Bringing all research under a single coordinating body would additionally serve to minimise the impact on the affected populations.

A significant proportion of the global population, particularly in western Europe and America, obtain electricity from nuclear sources. Had the Chernobyl accident occurred there and affected those populations, they would have expected to be compensated, either individually or on the basis of a national health care programme. Given the economic circumstances in the former Soviet Union, those exposed have little chance of compensation but would benefit from international help to obtain adequate treatment. The global community needs to learn from their experience: those who benefit from the production of nuclear electricity should finance an independent international foundation to coordinate research and provide humanitarian aid.